FARMVILLE, Va. — Democratic nominee Tim Kaine opened the first and only presidential debate by hammering home the message that Republican presidential nominee Donald Trump is reckless and can’t be trusted as commander in chief.

Mr. Kaine said that the issue hits home with him and his wife because their son is deployed overseas in the Marine Corps.

“We trust Hillary Clinton my wife and I with he most important thing in our lives,” he said, sitting across of conference table from Republican vice presidential nominee Mike Pence. “We trust Hillary Clinton as president and commander in chief, but the thought of Donald Trump as commander in chief scares us to death.”

The opening jab underscored how Democratic nominee Hillary Clinton’s camping has gone on offense since her winning performance in the first presidential debate last week. They were looking to Mr. Kaine to close the deal.